In general, an apparatus for measuring a thickness change measures the thickness or a thickness change of a thin film.
The thickness of a thin film is conventionally measured by using two representative methods described below.
The first is a method of monitoring a thickness change in real time by measuring the amount of deposition by using a crystal oscillator sensor. However, since the crystal oscillator sensor has to be replaced frequently, accurate calibration is required, and the crystal oscillator sensor is saturated and shows a non-linear result if the deposition exceeds a certain amount, the above method may not easily monitor the thickness change in real time.
The second is a method of measuring the thickness of a thin film after the thin film is completely deposited. For this, various schemes such as ellipsometry, a white light interferometer, alpha-step, and a laser triangulation system may be used according to a material of the thin film. However, if the thin film has a thickness of about 10 nm, the thickness may not be easily accurately measured. Even when a thickness of 1 μm is measured by using the above method, there may be various problems in, for example, preparing a sample or other factors.
Also, since an optical system such as confocal optics requires a high level of precision in order to increase the accuracy of measuring the thickness of an ultra thin film, precise alignment is demanded and thus the price of overall parts or components is inevitably increased.